This invention relates to a hydraulic auxiliary power steering system applicable to automotive vehicles in particular as well as to marine craft.
Generally, the auxiliary power system includes a mechanical connection between the manually operated mechanism or steering wheel and the steered parts of the vehicle such as the traction wheels or a rudder, in addition to the power reinforcement provided by a source of auxiliary power. In one type of such auxiliary power steering system, a pressurized fluid supply always provides the maximum operating pressure required. A control valve is provided having a closed, central position blocking the discharge line from the high pressure pump. When there is no steering action, only leakage fluid flows through the control valve under the maximum pressure to which the pump is limited by a pressure limiting valve. Also, upon attaining maximum pressure, the fluid delivered by the high pressure pump drains into a reservoir tank. Both of the foregoing processes are accompanied by considerable fluid losses. Further, the maximum pressure is not necessary for most steering operations especially steering during vehicle travel. Therefore, there is an energy loss because of the lower level of energy required for most steering actions.
It is therefore an important object of the present invention to provide a hydraulic auxiliary power steering system wherein its fluid power supply in a state of rest when no steering action occurs, generates a low pressure as compared to the customary high operating pressures provided during steering action, the low pressure being increased, however, during a steering action to the required value.